In order to obtain light of a desired wavelength by altering the wavelength of light emitted from a light emitting element in an optical semiconductor device such as a light emitting diode (LED), sealing or coating the aforementioned light emitting element by means of a curable silicone composition that contains a phosphor is a known technique (see Japanese Unexamined Patent Application Publication Nos. 2002-314142 and 2004-359756).
However, curable silicone compositions that contain phosphors are such that the phosphor can precipitate and separate during storage and the phosphor can precipitate and separate due to the viscosity of the composition being lowered when the composition is cured by heating, meaning that the obtained optical semiconductor device can suffer from problems such as color unevenness or chromatic shifts. As a result, a proposal has been made to additionally use nanoparticles in order to suppress precipitation and separation of a phosphor in a curable silicone composition (see Japanese Unexamined Patent Application Publication No. 2011-222718).
However, curable silicone compositions that contain both phosphors and nanoparticles exhibit a significant reduction in fluidity, meaning that problems can occur, such as variations in discharge amount during potting and sealing or coating of a light emitting element being unsatisfactory.
An objective of the present invention is to provide a curable silicone composition which has excellent fluidity and which is cured to form a cured product in which phosphors are homogeneously dispersed and which has a high refractive index. In addition, another objective of the present invention is to provide a cured product in which phosphors are homogeneously dispersed and which has a high refractive index and to provide an optical semiconductor device having little color unevenness or chromatic shift.